The incident occurred at 6.24 pm, state media reported. Wheel-chair-bound Ji Zhong Xing set off an explosive said to be made of gun powder used in fire crackers as an airport security guard approached him at the arrival hall inside the BCIA’s -- among the world's busiest airports -- terminal 3.

Reports said he was protesting at being ill-treated by the police. According to BBC, an online microblog attributed to him suggests his lower body was paralysed after he was alleged to have been heavily beaten by security agents in southern China in 2005.

There was no statement from the government about Ji's motive.

State media reported that Ji was the only one to be injured in the explosion that was followed by billowing white smoke that spread after the bomb was triggered.

Security and medical personnel rushed to the scene of the incident as the area was quickly cordoned off.

The news of the incident spread rapidly on China’s Twitter-like Weibo services with eyewitnesses posting photographs and comments within minutes; the incident was reported online much before state media confirmed it.

One photo, which was reposted several times, showed Ji sitting on a wheel chair and waving his hands; it showed him holding a packet.

Earlier, Ji had wheeled himself into the airport while distributing handbills to people waiting around.

Soon after, security guards walked up to him and stopped him from distributing the pamphlets. Ji then went to another part of the terminal and began to scream and shout.

It was then, according to Weibo accounts, he took out the packet and detonated the explosive using a trigger. Ji was taken to a hospital where he is undergoing treatment.

A policeman takes samples at an area where a man on a wheelchair set off a homemade bomb at Beijing International Airport's Terminal 3 in Beijing.(AP Photo)

Mass protests especially on issues of environment are common in China. But individual protests like the one on Saturday evening is rare except in areas ethnic Tibetans – nearly 120 of them – have self-immolated protesting against what they perceive as Beijing’s hardline rule.

The incident on Saturday coincided with the arrest of six urban management officers –para-police force tasked with enforcing municipal bylaws and maintaining urban order – involved in a violent clash with a watermelon vendor that led to his death last week.

Deng Zhengjia, a 56-year-old farmer died after being assaulted by the suspects last Wednesday.

The fight occurred after Deng and his wife tried to sell watermelons at a tourist spot where urban management officers had banned such activity, state media reported.

A witness to an explosion is mobbed by journalists at Beijing International Airport's Terminal 3 in Beijing. (AP Photo)